Piston cooling



Feb. 13, 1951 L. E. ENDSLEY PISTON COOLING Filed March 19, 1948 INVENTOR LOUIS E. ENDSLEY ATTORNEY Patented Feb. 13, 1951 Price PISTON COGLING Louis .E. Endsley, :Bittsburgh, Ba., .assignor to Fairbanks, .Morse & 00., =Chicago,.-Ill.,.a cor-110'- .-ration of Illinois Application 'March ili), 1948, Serial *No. 15,941

.31Claims. (Cl. 123- i1.38)

1 This invention is concerned with the cooling of pistons and'isparticularlyexemplified by novel ieaturesof construction and arrangement toennb1e a5more-efie0tive cooling of pistons and the like.

A'particularly important objective of the pres-- .idivided into-a head end and a skirt'end-chamgber, and towsupply and control the flow 'or cirrjculationlof :the cooling medium such that it "can absorb a maximum of heat in the head end :chamber, :then move to the skirt end chamber and eventually be discharged, the control of the :circulation of the cooling medium being accomplished in .part through the aid of the physical :arrangementcf the piston parts-and in part by the forces to which the cooling medium is :subiiccted :during piston operation.

Inaccordance with-the above stated object, the preferred piston construction embodies the important featuresof supplyingthe cooling medium to the head end chamber, there causing a great degree of turbulence and cross flow more per- *tectly to bring the cooling medium into intimate contaot'with the heated surfaces :for heat transfer therebetween, contmlling the rate of discharge or removal of thecooling medium toward "the 'skirt endchamber such that the head chamber is maintained substantially one-half full of theooling medium, and causing a complete change of cooling medium in the-piston by regu- :latingfthe final "discharge from the skirt chamber esuchf'tha't the residual body of cooling medium itherein will not adversely oppose the flow of medium. out 'of the 'head chamber under the influences "of forces to which the cooling medium subjected during piston operation.

IFur ther objects and attendant advantages will appear from the following description "relating-to a presently preferred embodiment of the inventlonxas the same 'is illustrated in the accompanying drawing, wherein:

Fig. '1 :is a longitudinal, sectional elevational view of the piston assembly in which the important characteristics of structure are shown:

Fig. 2 is a top view in section of the present 'the "view :being taken at :line 2-2 in Fig. :-1,-'and Fig. 3 is ail-enlarged and fragmentary sectional view of a typical flow controlling orifice opening between the respective piston chambers, the view being taken at line 3i3 in Fig. 2.

In the drawing, the piston It best illustrating 'the characteristics of construction and arrange- :ment, is seen .to include aihollow, cylindrical body having a skirt wall ll integrally formed with a crown wall ['2 of semi-spherical configuration. The skirt wall H is formed with an upper thickened band or wall zone H3 in the outer surface :of which suitable grooves are formed to receive the piston rings, and a lower, thickened band or wall zone 14 adjacent the .open end thereof and in the outer surface of-which grooves are :formed to :receive other piston rings. The crown wall 12' of the piston body is provided at its under side with .a'plurality of depending elements arranged "in inner and outer groups or series l5 and-"i6- respectively. These struts are each arcuately shaped, and the groups thereof are substantially concentrica'ly related and extend parallel with the longitudinal axis of the piston to.

More specifically, the inner series of arcuate elements [:5 are arranged in circumferentially spaced relation to define a central :crown'pocket H which opens at the slot-like ports [:8 :(four such ports being indicated in Fig. .2) to theannular space -19 defined by the outer series of circumferentially spaced elements it. The disposition of elements It .is .suchtha't an outer annular cavity 29 is formed between each thereof :and theupper adjacent zone of the skirt-wall II. The elements 1.6 also provide slot-like ports 21 therebetween-which-are staggered relative to the ports .ls'betweenthe inner series of elements l5. In the casting of this piston body, the outer ele-.'- ments [6 areeach connected with the thickened skirt wall 'zone I3 by means of a boss 22, these :bosses beingopeniacross the-top so thatithe outer annular cavity 26 is uninterrupted in its upper peripheral zone adjacent the skirt wall :lfl an the under side ofthe crown wall 112.

The present piston assembly (Fig. 11) :also includes an insert member 25 formed "to provide an upper fiat face 26 bounded by the flange '2 which is adapted to engage the skirt I I at the annular, shouldered. seat 28 machined into the thickened wall zone I3. The lower endo'f the member 25 is'characterizedby the flange 29 adapted to have a :close sliding fit with the inner "surface of the thickened skirt-wall zone I4. Intermediate the :ends of the member 25, suitably formed and spaced bearing boss formations 31] are provided 'to "receive the write pin 31. In turn, the pin 31 engages in the bearing bore of the upper end 32 of the usual connecting rod member 33. As shown in Fig. 1, the insert member 25 is spaced from the skirt wall I l to define an annular skirt chamber 35 which is closed, to the extent hereinafter to be described, by the flanges 21 and 23.

The assembly of the several parts of the present piston is believed obvious, when it is understood that the securing studs 31 threadedly engage in the upper bosses 22 of the body, extend axially through a drilled bore in longitudinal bosses 39 of the insert member 25 and are engaged by nuts 38 at their free ends. Further, and before assembly, each of the struts l and i6 is machined across its free end to a common plane which is coplanar with the seat 28 in thickened zone l3 of the skirt wall ll. ton assembly is exemplified by the provision of a crown or head end chamber above the fiat end face 26 of the insert member 25, and the skirt end chamber 35 below this face 26.

Cooling medium for the piston it is supplied from the crankshaft lubricating system (not shown) through the bore 40 in the connecting rod 33, and the annular groove 4! in the rod end portion 32 to the outlet passage 52 at the upper zone thereof. The cooling medium or coolant passes into the central crown cavity I! byway of the enlarged port 43 at the face 23 of member 25. An annular sealing ring 44 is adapted to bear upon the rod head 32 under the loading of a suitable spring 45 and prevent leakage of the coolant away from the piston crown chamber. The coolant (engine oil in this case) entering the crown chamber in the zone of the central cavity I1 is under pressure and thus possesses a velocity component which causes its rapid flow outwardly of this cavity I! through each of the several slot-like ports I 8 between the inner series of elements l5. In treating this pressurized flow of coolant which reaches the central cavity II, it is highly important that no stratified flow trends develop in the crown chamber which could cause an inequitable heat absorbing contact of the coolant with the piston crown areas which receive heat from the combustion or firing side of the crown I2. This hazard is eifectively overcome 'by arranging the ports is of the inner series of elements I5 in off-set or staggered relation relative to the ports 2| of the outer series of elements l6. Thus, the coolant is compelled to leave the central cavity I! in a plura ity of paths or streams, and in like manner is compelled to leave the annular cavity [3 in a plurality of paths or streams which are not directly in the line of the first created flow paths. The coolant must then traverse a course to the outer annular cavity 20 which requires a change in direction of flow. Hence, the cooant in the crown chamber is forced to contact substantiallyall of the heated surfaces of the piston crown and depending elements, and in the process :a beneficial degree of turbulence is established whichincreases the rate of heat transfer from the metallic body to the fluid coolant.

The body of cooling fluid supplied to the crown chamber of the piston is discharged to the annular skirt chamber 35 by way of a plurality (four being shown in Fig. 2) of restricted orifices 41; These orifices or transfer'ports 41 are located in spaced pairs, each pair being in diametrically opposed relation,- and in the upper peripheral flange 2'! of the insert member 25 in the; zone of the outer annular crown cavity 2!] between adjacent stud receiving bosses; 22. .The

A characteristic of this pis- 4 coolant passing to the skirt chamber by Way of these orifices 4! is eventually discharged to the crankcase (not shown) by a suitable discharge opening or spitter passage 48 provided in the lower flange 29 of the insert member (Fig. 1).

The cooling of a piston having the above described physical characteristics is predicatedupon the important principles that the coolant admitted to the crown chamber should be allowed to remain in contact with the hot metal surfaces sufiiciently long to absorb a maximum of heat, that the rate of heat absorption can'be materially increased by the turbulence of the coolant and its rapid flow over the heated surfaces, that the heated coolant should be discharged as quickly as possible with a min mum of impedance to its fiow, and that the coolant should be completely changed as frequently as possible. In keeping with these principles, the present piston construction is so designed that a body of coolant is maintained in the crown chamber equal approximately to one-half the crown chamber volume. Maintaining this volume of coolant in the crown chamber is accomplished by selecting an orifice diameter which approximately balances the rate of fiow outwardly of these orifices With the rate of supply of fresh coolant at port 43, and by forming each orifice (Fig. 3)v witha rounded lip zone 49 facing the crown chamber and a relatively sharp lip 50 at its opposite end so that the flow toward the skirt chamber 35 is relatively less retarded than flow in the opposite direction. It is desired that a portion of the coolant flowing into the skirt chamber 35 re:-

. turn to the crown chamber under inertia forces of piston movement to enhance the turbulent character of coolant movement in the latter chamber. But at the same time more coolant must be moving away from this crown chamber than is returned to it to maintain the desired volume of coolant therein, and to balance the volume of fresh incoming coolant. Further assistance in respect of maintaining thevolume of coolant in the crown chamber is atta ned by proper selection of the size of the final discharge or spitter' port 48 in the lower flange 29 of' the member 25. While only a single spitter port :43 has been indicated, it is possible to provide a plurality of such ports. In either case, the effective area of the port, or ports, should be calculated on the basis that coolant to a depth of approximately one inch in the skirt chamber when the piston is on crank end center is most desirable. This quantity of coolant wi l reduce excessive reverse flow of coolant toward the crown chamber when the piston reaches its head end center where the inertia forces on the coolant attain a maximum. s

In operating a piston of this character, there will be periods in the cycle of motion'whenthe coolant flows outwardly from the central cavity H, otherperiods when this flow is reversedggand still other periods when the fiow'is either of these combined with a fiow'into or out of the crown chamber. Thus the coolant ismade to attain a high degree of turbulance in the zone of highest temperature and more perfectly contact the hot metal surfaces with a marked increase in the rate of heat absorption. The elements [5 and 16in this crown chamber further control the coolant flow, increase its equitabledistribution throughout the chamber area, and generally act'and'perl form the function of bafllesfl v I The foregoing. .descriptionlhas .beenlgiven in connection with a presently preferred pistoniassembly, however it is not the purpose to limit the scope of the invention precisely to that which has been disclosed, as it is entirely possible to have substantially equivalent structural features for attaining a similar cooling result without departing from the spirit and full'intent of the claims hereunto appended.

What is claimed is:

1. In a piston of the character described, a piston body having a crown and a skirt, a member disposed in said body and cooperating with the latter to define a chamber adjacent the crown and a chamber between the body skirt and memher, said memberhaving a plurality of ports opening between said crown and skirt chambers and a passage opening from the skirt chamber to the exterior of the piston, and a connecting rod operatively connected with said member and provided with coolant feed passages opening to said crown chamber, said ports in said member being formed with a curved lip at the crown chamber end thereof to permit the passage of more coolant from the crown chamber than is induced to reenter from the skirt chamber due to forces to which the coolant is subject during piston operation, and the passage opening from said skirt chamber being of such area as to limit the volume of coolant collecting in the latter chamber.

2. A p ston comprising a body having an integrally formed crown and skirt, a member positionable in said body and cooperating therewith to define a crown chamber and a skirt chamber, said member having a coolant inlet port opening centrally of the crown chamber, a plurality of spaced orifices opening between said chambers, and a spitter passage opening from said skirt chamber, and a plurality of balile means arranged in said crown chamber to define intercommunieating crown cavities through which coolant flows, each of said orifices having a curved lip at the crown chamber and a relatively sharp lip at the skirt chamber, and the combined areas of said orifices being chosen such that the flow of coolant into and out of said crown chamber is regulated to maintain a coolant volume therein 3. In a piston of the character described, a body having crown and skirt portions, a member positionable in said body to cooperate therewith in defining a crown chamber and a skirt chamber, baffle means arranged in said crown chamber and adapted to define a plurality of interconnected passages between the central and peripheral zones of the crown chamber, said member being formed to provide a coolant inlet port for the crown chamber, transfer ports opening between said chambers, and an outlet port opening from the skirt chamber, and means operatively associated with said member for supplying coolant to said inlet port for admission to the crown chamber, said transfer ports being formed with a rounded lip at the crown chamber end and a relatively sharp lip at the skirt chamber end whereby the fiow of coolant from the crown chamber toward the skirt chamber is relatively less restricted than in the reverse direction of flow, and said outlet port being of a size to discharge the coolant from the skirt chamber at a rate less than that which would maintain the skirt chamber substantially empty during piston operation.

LOUIS E. ENDSLEY.

REFERENCES CITED The following references are of record in the Endsley et a1 June 7, 1949 

